In the field of animal husbandry, mankind is continually seeking to improve livestock by the selective breeding thereof. Artificial insemination of livestock has become a common practice and is being used on an ever increasing scale for selective breeding and to take advantage of genetics available from many outstanding herd sires without the investment of owning these herd sires. Breeding by artificial insemination requires that the semen be administered while the female is in estrus. In more recent years, embryo transplants have been used to take advantage of desirable genetics in an outstanding female to increase many fold her produce, and to examine in a short span of time, i.e. one year, the transferable genetics of a herd sire to see if he breeds true, i.e. he reproduces a likeness of himself, vis-a-vis color, polled, height, etc.
Such embryo transplant programs require that all the recipient cattle that are to receive embryos on a certain day be in the same heat cycle as the donor cattle being collected on that day. Again, it is required to know the true estrous cycle of both the donor and the recipient cattle so that synchronization of the estrus cycle can be accomplished through the administering of drugs.
The most common approach in determining whether an animal is in heat has been visual observation by herdsmen, usually aided by a "teaser" or "gomer" bull or "teaser" female. These "teaser" or "gomer" bulls have been surgically altered so they cannot service a female, but they can detect estrus. "Teaser" females have been given male hormones to make them behave like a bull and to enhance their detection of estrus in normal females.
The visual signs that indicate heat cover a wide range. Under normal conditions, a cow in heat (estrus) will stand for a limited time, usually measured in seconds, and accept service by a bull or stand to be mounted by a "teaser" animal. In addition, in peak estrus a female will stand and permit herself to be ridden by other females, or she will attempt to ride other females not in estrus. Such females not in estrus will usually quickly "run out from under" the female in estrus. The visual method of detecting heat is wholly dependent on these homosexual tendencies of the female in estrus and by other "sympathetic females" not in estrus. Moreoever, animals when in heat become more active and nervous. They have brighter eyes, are restless and may sometimes bellow. Often a female may walk in search of a bull. Another sign that a female cow is in heat is that the visual genital organ, the vulva, becomes somewhat swollen and excretes a clear discharge. Additionally, cows that have recently been ridden show suggestive marks. For example, the hair over the tail head is disturbed and raised. Moreover, the fore feet of the riding animal may leave marks on the sides and shoulders of the ridden female. Further, if "teaser" animals are fitted with a "chin ball" a marker containing a dye, this dye will be deposited along the spinal chord of the animal ridden as the "teaser" uses the strength of its neck and chin to mount the cow in estrus.
When estrus occurs, the cow will show an increased tendency to stand and permit herself to be mounted by other animals as hereinabove stated. When the mounted animal allows the mounting animal to remain for about five to eight seconds, a "standing heat" has occurred. The most frequent mountings occur by bulls or "teaser" animals. Accordingly, the repeated mountings of a cow by an animal of either sex and for a time interval regarding each mount of about five to eight seconds is a good indication that the frequently mounted cow is in peak estrus or in "standing heat". The normal estrous period usually lasts from about twelve to eighteen hours, with peak estrus being about six hours.
The above-identified visual inspection and observation techniques of the herd require constant observation of the herd to determine whether an animal is in heat. Such visual observation must be conducted frequently and must be accompanied by immediate identification and/or segregation of the animal in heat if it is to be artificially inseminated. Also, unless the herd is maintained under constant visual observation, estrus may go undetected in many animals that never "peak" but maintain a low but constant level of estrus for a number of hours, and such low level estrus can only be detected by a bull or "teaser" animal. Visual observation of the herd is further made difficult, since many animals are nocturnal, particularly cattle, and their increased night sexual activity goes undetected. Most experts agree that approximately 68% of estrus in cattle occur after 6:00 p.m. and before 6:00 a.m. with 43% occurring between midnight and 6:00 a.m. Therefore, unless 24-hour visual observation of the herd is maintained by dedicated personnel, heat detection is inaccurate, inefficient, and depends largely on the ability and experience of the herdsmen, which usually is lacking. If the herdsman is not skilled in observing these visual signs, he can easily miss the occurrence of heat. Further, inclement weather may deter his observation regardless of his dedication and ability. These problems make it difficult to optimize breeding of the herd annually so that the offspring are born within the same "time window", mature at approximately the same time, and are ready for market or to be bred themselves at a common time.
Various devices and systems have been used or described for improving the efficiency of the detection of estrus. A commonly used device is a marking device such as identified in U.S. Pat. No. 1,237,983 issued to Werner on Aug. 21, 1917, and entitled "Marking Device." Other such marking devices utilize a tube or capsule mounted on the tail head of the cow. The tube contains a suitably colored dye. When the cow is ridden, the tube or capsule breaks and the dye is spread over the tail head of the cow. Such devices are passive in nature and are activated by pressure from the brisket of the mounting animal. While such devices have been somewhat satisfactory, these devices still require observation by the herdsmen. Moreover, careful visual observation is necessary in order to determine if the dye mark is fresh or old. Further, the presence of the dye mark merely indicates that a mounting has taken place. The mere fact that a mounting has taken place does not provide a true indication of whether the animal is in estrus, because standing heat requires that the mounting has occurred for about five to eight seconds and mountings have generally been repeated many times. Some cows in intense heat permit themselves to be ridden up to fifty times in a twelve to eighteen hour period. Other cows permit rides only a few times and of short duration.
U.S. Pat. No. 4,239,018 issued to Griffin, et al. on Dec. 16, 1980, and entitled "Heat Detector for Livestock" discloses the use of a delayed release pressure sensitive device for releasing a dye only after sustained pressure from the mounting animal has been achieved to minimize false triggering associated with prior passive marking devices. However, the Griffin, et al. device is also dependent on visual observation.
An additional detection apparatus is described in U.S. Pat. No. 3,297,020 issued to Mathiesen on Jan. 10, 1967, and entitled "Apparatus for Detecting Estrus in Animals." The Mathiesen device describes the use of a vaginally inserted electric probe for detecting accelerated mucous secretion accompanying the onset of heat. A visual indicator is utilized with the Mathiesen device and does not overcome the deficiencies previously mentioned. Further, the insertion of a foreign object into the vulva of a female animal fosters disease and infection.
U.S. Pat. No. 3,844,273 issued to Polson on Oct. 29, 1974, and entitled "Method and Apparatus for Animal Heat Detection and Recording" further discloses an additional system for the detection of heat in animals. The Polson system discloses an electronic system comprising a radio transmitter individually mounted on the female animals. The transmitter includes switches which are activated by the mounting animal. Again, as in those devices utilizing marking systems, the Polson apparatus merely indicates that an animal has been mounted but provides no indication of the duration or frequency of mounts and, therefore, no indication of whether the mounted animal was in standing (peak) heat.
U.S. Pat. No. 4,206,766 issued to Bielka on June 10, 1980, and entitled "Apparatus for Detecting Animal Estrus" utilizes a pressure responsive device connected to an indicating device to indicate the presence of estrus in an animal. A predetermined pressure must be exerted on the pressure-responsive device prior to release of the device in order to prevent spurious releases of the indicating device caused by pressures which are less than those occurring during an actual mounting, such as those caused by a second animal resting its head on the pressure responsive device. Even though spurious releases may be prevented by the Bielka apparatus, a false indication of heat may be indicated if sufficient pressure is available such as rubbing against a tree limb.
A need thus exists for an apparatus for determining when an animal is in estrus which provides a reliable indication of standing heat. Such a system must provide an indication that the female has been mounted and the duration and frequency of the mountings to provide a true indication of whether the animal is in estrus and the exact time of peak estrus. Such a system, to ensure reliable and accurate measurements must not rely upon a visual indication of the condition of the animal, since such visual observations have shown to be unreliable and difficult to routinely accomplish.
Although the present invention has application for determining when an animal is in estrus, the present system can also be utilized for other aspects of herd management including the administering of medical treatment and the dispensing of feed. Therefore, as will subsequently be described, the present invention also provides for other herd management functions.